Staff Article

The Florida Keys boast the largest living coral reef in the Western Hemisphere.  This unique phenomenon lies about six miles offshore in only 20 to 30 feet of water and stretches from near Miami in the Atlantic Ocean southwest along the Keys in the Florida Straits and out to the Dry Tortugas in the Gulf of Mexico.  The shallow waters surrounding the Tortugas, warmed by the Gulf Stream, provide snorkelers with an almost unparalleled view of the reef.

We have all heard about the reef, its fragility and its beauty, but just exactly what is it?  Where did it come from?  Why do we call it a “living” reef?  The reef, properly named the Florida Reef, is made up of layers of calcium carbonate secreted by coral polyps over a period of several thousand years.  The polyp is tiny and soft-bodied.  New polyps are constantly being grown by the reef, but at the rate of only about one half inch per year.  Each polyp contains algae called zooxanthellae, which gives coral its color.  The zooxanthellae takes in carbon dioxide, processes it and gives off oxygen that the polyp needs to stay alive and create coral.

Touching the coral can destroy the polyp and leave the coral susceptible to bleaching and disease.  That explains why a ship going aground on the reef is such an ecological tragedy.  Today’s snorkelers and scuba divers are cautioned to look but don’t touch.

Seagrasses and mangroves are important to the coral ecosystem that includes the reef.  Mangroves have roots that sink to the bottom of the ocean and provide a breeding ground for birds and marine life that migrate to the reef as they mature.  They also provide nutrients and filter pollutants from the landbase.  Seagrasses provide foods and serve as a nursery for pink shrimp and lobster among other sea life.  They also release necessary oxygen.

You can find out more about the complex interactions of the nearshore ecosystem of reefs, seagrass, and mangroves from our onboard naturalists on your journey out to the Dry Tortugas. 
They will be happy to give you pointers on what to look for as you snorkel the beautiful coral
growth around Fort Jefferson.